Microwave scanning system and method



Dec. 4, 1951 G. 1 FERNSLER 2,577,17

MICROWAVE SCANNING SYSTEM AND METHOD Filed July s1, 1947 Eig.l scam/wma f V/.T/laf:

lie-HECTOR ANTENNA 4/ AMPL /F/ JH/lPl/VG CIR C Ul T :inventor Gear eLFerlzsIer en l Il',

Gttorneg Patented Dec. 4, 1951 NHCROWAVE SCANNING SYSTEM AND n METHOD George L. Fernsler, Lawrenceville, N. J., assigner to Radio Corporation of America, a corporation of Delaware Application July 31, 1947, Serial No. 765,037 l 13 claims. l

` This invention relates generally to microwave propagation systems and methods and more particularly toY improved methods of and means for changing the azimuth or elevation angle of a parabolic microwave antenna system without changing the physical position of the parabolic reflector.

It has been customary in microwavepropagation systems to utilize a horn type or ared radiator'type wave projector operating into a parabolic reflector which is employed primarily to improve the directivity of the radiated beam. For example, a rectangular waveguide system operating in the TEoi mode may be employed with a matching section preceding a horn wave radiator, the horn opening toward a transversely disposed plane reflector to project the radiated beam to a parabolic reflector which thereby improves the directivity of the radiating beam. In previously employed systems, the position of both the radiating horn and the beam reector have been changed to provide variation ofthe elevation or azimuth angle of the propagated energy. Mechanical displacement of relatively large mechanical elements required in such systems is relatively diflicult and expensive and requires` tion prior to its projection toward the parabolic reflector structure.

In accordance with a first embodiment of the invention, an elbow of a matched section of waveguide opening into the horn radiator includes a wave reflecting element or diaphragm reflector, the position of which may be changed by the action of a lsolenoid or a mechanical actuating mechanism. Changing the 'position of the waveguide reecting element changes the directivity of the microwaves radiated from the microwave horn. thereby changing the radiating beam projected from the parabolic reiiector. .Y Since movement of a wave reflecting element in a transmission waveguide structure causes variations in the impedance characteristics of the transmission waveguide, a tuning element preferably is included in the transmission waveguide and synchronized with the movable wave reflector to provide substantially constant microwave transmission characteristics.

The second embodiment of the invention employs a section of transmission coaxial line or waveguide, including microwave radiating elements, which is arranged to rotate in an arc with respect to the balance of the microwaveY coaxial' line or waveguide transmission system. Thus a fixed parabolic reiiector disposed adjacent to the movabley wave radiating element will project a microwave beam through a variable angle in the plane of motion of the movable microwave radiator. A variable control element, such, for ex- Iample. as a variable resistor, ksynchronized with the motion of the arcuately adjustable radiating element, controls a pair of solenoids which actuate electromagnetic tuning elements operable to interpose suitable reactance into the main transmission line to compensate for variations in the impedance of the line due to the arcuate motion of the radiating portion of the system.

Among the objects of the invention are to provide improved methods `of and means for scanning a predetermined spacial region by microwave energy. Another object of the invention is to provide an improved method of and means for radiating a microwave beam through a predetermined elevation or azimuth angle. An additional object is to provide an improved method of and means for employing a relatively fixed parabolic wave reflector for radiating a variably directional microwave beam. A further object of the invention is to provide improved methods of and means for` radiating a microwave beam through a variable elevation or azimuth angle by varying the directional characteristics of a microwave beam projected toward a relatively Xed parabolic microwave reflector. Another object of the invention is to provide improved methods of and means for radiating a microwave beam through a variable elevation orv azimuth angle by varying. the directional characteristics of a micro- Wave beam projected vtoward a relatively fixed parabolic microwave reiiector and including4 means synchronized withl the variable directional radiating means for providing constant impedance characteristics in the transmission system.

The invention will be described in greater detail by reference to the accompanying drawing of which Figure 1 is a schematic circuit diagram of a rst embodiment of the invention, Figure 2 is a schematic circuit diagram of a second embodiment of the invention and Figure 3 is a fragmentary schematic view of a modification of saidv first embodiment of the invention. Similar reference characters are applied to similar' elements throughout the drawing.

Referring to Figure 1 of the drawing, a first embodiment of the invention utilizes a movable diaphragm wavereflector I atan elbow 3 of af waveguide 5 connecting a microwave generator 'I to a microwave radiating horn 9. The mouth of the horn 9 faces a plane wave reflector II which reflects the radiated waves back to a parabolic reflector I3 which effectively focusses the radiated waves in a parallel beam I5.Y The movable reflector I is' pivct'edl at thepoint I1 and may include a corrugated Sylphon bellows joint I9 on the opposite face thereof. The movable diaphragm reector I is actuated by a solenoid 2| to which is applied a sawtooth oif'sinel wave' voltf age derived from a scanning voltage source 2'3.

Movement of the diaphragm-.reflector I in response to the scanning voltagev as indicated by' the arrow 25, changes the effective angle o the microwaves radiated from the mouth of the horn 9, thereby varying, either' in a vertical or horizontal plane, the radiation angler of the focussed microwave beam I5. rlhe device may be arranged to Vary either the elevation or azimuth angle of the radiated microwaves, and if desired, two. elbows and movable diaphragins may be employed to vary both angles in any predetermined. pattern. The scanning pattern in either plane isl determined by the wave form of. the

Vthe generator portionof the waveguide and by utilizing. a transversely movable tuning plunger. 29.' adjacent tothe matchingdiaphragm 2l. The position of the tuning plunger on the transverse axis ofthe waveguide'v 5 may be controlled by a.

second' solenoid 3| actuated in. synchronisrn.- with the pivotedlrefiector I.

IThe scanning voltage source 2'3` is connected through an. amplifier $3 anda wave-shaping. circuit. tev energize the. second solenoid? 3i and tlius actuate the tuning, plunger 29( vdesiredphasel and synchronism.. with the pi'voted reector I. The wave-shaping circuit 35i's` optional since-- itin'ay be desirable toV actuate the tuning-,plunger bytlie same type ofl scanning voltage waveform actuates the movable reiiec'tor".

desired' for actuation ofthe tuning plunger;l the desired. change in waveworm may be provided by the4 wave-shapingcircuit 351 From the foregoing description, lit' is seen-that'.

the elevation or azimuth angle ofy radiated microwaves may be varied irl-any desired manner with'- out moving any of the cumbersome-microwave radiating-I or reflecting apparatus. Theonly movable elements' required` are a smalllight diaphragm forming one of the walls" o'f the transmission waveguide"structureandA a' tuningplungerv synchronized' with the' niovablediaphragm.. it' shouldy be understood' that the tun"- ing plunger' and pivoted reflector may besynchronized by purely mechanicallinkages instead ofby the electrical linkageA described heretofore.

andV that other types orI variable tuning. devicesv may be. substituted. for the solenoid-actuated tuning lunger described.

Figure 2 illustrates a second embodiment'of the invention wherein the. microwave' generator` 1 f is connected through" a coaxial transn'iiss'iori line' A piane renector Il" 5" to a dipole antenna 41;

However, if a diierent type of scanning voltage W'avei'rin is' `Vble contact 5I of avariable resistor 53 to vary the voltage frcmfabattery applied to the input circuit of an amplifier 51. The output circuit offthe amplifier 5'? is applied to a pair of ampliiier wave-shaping circuits 5g, EI. The output circuits of the amplier wave-shaping circuits 59,. 5i are connected respectively t0 a pair of solenoids E3, 'ior actuating a pair!V of tuning plungers El, cxtendin'g'into theA niain transmission line 5. Preferably the tuning plungers 61.69 are separated by a distance ofthe order of 3/8, wavelength' at the operating microwave frequency inorder that they may provide the desired reactive effect upon the transmission line to match the antenna t thel mici' wa've transmitter for ally positions of thefriiovaible' a'ntenna system.` A bearing'A-cntactii at the" end of the inner conducter i3 of thernaii trans'- mission line 5fv provides siiit'alileA- electrical contact between the main transiifl'issionV line and the" rotatable center conductor' of the antenna transmission line. y

if desired, the. parabolic reiector t 3 may be fixed. with' respect to the main transmission lineY 5', the antennaportion 43 off the movable porftionof'k the" vtransmission line being movable' through the desired-i small elevation or azimuth angle in a slot'l3` in the parabolic ree'ctor i3".A rthe planereflector I I would be movable with theU antennaA 44 The enibodirnentof'mthe invention describedl by reference to Figure 2 of the drawing utilizes a.l

properly. designedr.rinwaccordance with knowntechnique, to provide the desiredelcctrical wave sha-pe forV actuating. the :tuning plungers 5Fl 69 in proper phase relation with` movable antennasystemI sothat theantennaiseffectively matched to -the microwaveftransmitter under alloperatingconditions.' K

Figure-'3 illustrates-a typicalmeclianical modification of the-first embodiment of' the invention, described.. heretofore by reference to Figure 1',

vvlerein`- ther movable' diaphragm reflector I co`u`1'ileolil tlir'oiigli'V a'- mechanical linkagev to Vthe tuin., plunger-'291 Movement of the diaphragm reflector I in the'direction-indicated by' the arrow pivot-ed 'rjejfictor. itsiiouidf beU understood that th'e'mechanical"linkagethus describ'e'd'is used merely forthe purpose of illustration', and thatl various v otherrtypes ofliiika'ges arid/or carri arrangements:mayjbe substituted; te provide the" desiredbooper'ation between'vr the' rrovable :dia-r phragm and the tuning plunger or other tuning devices.

Thus the invention described comprises improved methods of and means for varying the radiation angle of a focussed microwave beam and for simultaneously and synchronously adjusting the microwave transmission characteristics between the microwave generator and directional Vantenna system to match the generator to the load under all operating conditions. The device may be utilized to vary either the elevation or Vazimuth angle of the radiated microwaves.

Either electrical or mechanical linkages may be provided between the microwave direction controlling element and the microwave tuning element to provide the desired cooperation therebetween.

I claim as my invention: l

1; A microwave propagation system including an antenna system having variable directional characteristics, a microwave signal circuit coupled through a transmission line to said antenna system, means including a rotating joint supporting said antenna for varying said antenna directional characteristics, adjustable voltage means operable simultaneously in response to and in synchronism with movement of said antenna and with said variation of said antenna directional characteristics, and adjustable tuning means for said transmission line separate from said directional varying means and responsive to said voltage means for adjusting the microwave coupling between said circuit and said antenna system to compensate for resultant variations in the output impedance of said antenna system as said antenna directional characteristics are varied.

2. Apparatus according to claim 1 including amplifying and wave-shaping means responsive to said voltage means and actuating said tuning means.

3. Apparatus according to claim 2 including solenoid means responsive to said amplifying and wave-shaping means for Vactuating said tuning means.

4. Apparatus according to claim 3 wherein said tuning means comprises a plurality of reactive devices operable upon the field of said transmission line.

5. Apparatus according to claim 4 wherein said reactive devices are spaced distances of the order of three-eighths of the operating wavelength along said transmission line. e

6. Apparatus according to claim 5 wherein said antenna'system comprises a resonant structure focussed by a substantially parabolic reflector.

7. A microwave propagation system including an antenna system having variable directional characteristics, a waveguide transmission line, a microwave signal circuit coupled through said wave transmission line to said antenna system, means including a movable reector in said line for varying said antenna directional characteristics, adjustable voltage means operable simul- 6 output impedance of said antenna system due to said movement of said rei-lector.

8. Apparatus according to claim 7 including a xed diaphragm in said waveguide disposed between said tuning means and said reflector.

9. Apparatus according to claim 8 including solenoid means responsive to said voltage means for actuating said reflector and said tuning means.

10. Apparatus according to claim 9 including amplifying and wave-shaping means interposed between said voltage means and said tuning actuating means.

11. Apparatus according to claim 7 wherein said movable reflector and said tuning means are mechanically coupled and movable together.

12. A microwave propagation system including an antenna system having variable directional characteristics, a microwave signal circuit coupled through a transmission line to said antenna system, means or varying the directional characteristics of said antenna system, adjustable control means operable simultaneously in response to and in synchronism with said directionalY varying means, and adjustable tuning means for said transmission line separate from said directional varying means and responsive to said adjustable control means for adjusting the microwave coupling between said signal circuit and said antenna system to compensate for resultant variations in the output impedance of said antenna system as said antenna directional characteristics are varied.

13. A microwave propagation system including an antenna system having variable directional characteristics, a microwave signal circuit coupled through a transmission line to said antenna system, means for varying the directional characteristics of said antenna system, adjustable voltage means operable simultaneously in response to and in synchronism with said antenna directional varying means, and adjustable tuning means forl said transmission line separate from said antenna directional varying means and responsive to said voltage means for adjusting the microwave coupling between said signal circuit and said antenna system to compensate for resultant variations in the output impedance of said antenna system as said antenna directional characteristics are varied.

GEORGE L. FERNSLER.

REFERENCES CITED The following references are of record in the 

